The present invention relates to a breather device for a power train (electric motor and gearbox) of an electric vehicle.
In a general vehicle, a gear case accommodating a gearbox (transmission, etc.) is provided with a breather device so that air within the gear case escapes to the outside through a breather chamber to prevent the air from rising to high temperatures and high pressures. Further, in an electric vehicle, a motor case accommodating an electric motor is also provided with a breather device to prevent air within the motor case from rising to high temperature and high pressure.
However, in this conventional electric vehicle, a breather device is provided for each gear case and motor case and the respective cases are enlarged in the size. Especially, an electric vehicle utilizing a fuel cell separately requires a supercharger, a large-sized radiator and the like in an engine compartment which accommodates the gear case and the motor case. Therefore, there is a need for each case to be rendered compact in size.
Accordingly, the purpose of the present invention is to provide a breather device for a power train of an electric vehicle which decreases the size of the gear case and the motor case.
According to a first aspect of the invention, there is provided a breather device for a power train of an electric vehicle including an electric motor and a gearbox connected to the electric motor. The breather device comprises: a breather chamber provided above a connecting portion connecting an electric motor housing and a gearbox casing; a first breather passage providing a communication between the breather chamber and an inside of the electric motor housing; and a second breather passage providing a communication between the breather chamber and a lubricating oil separation chamber formed in the gearbox casing.
Herein, the term xe2x80x9cgearboxxe2x80x9d includes a power transmission device such as a single stage reduction gear device, a multistage transmission, and a continuously variable transmission.
In this construction of the breather device, one breather chamber communicates with the inside of the electric motor housing and the inside of the gearbox casing through the first and second breather passages respectively so that air within the housing and the casing can escape from the breather chamber. Further, since the second breather passage is in communication with the breather chamber and the lubricating oil separation chamber, even if lubricating oil is splashed by the gears within the gearbox, the splashed lubricating oil is separated in the lubricating oil separation chamber so as to prevent the lubricating oil from entering into the breather chamber through the second breather passage. Further, temperature of the breather chamber drops abruptly after a long hour drive under a lower outer temperature. However, since the gears within the gearbox and the lubricating oil have large heat quantities, these heat quantities are absorbed by air within the breather chamber through the second breather passage and therefore temperature in the breather chamber decreases gradually.
According to a second aspect of the invention, the aforementioned breather device may be made such that a terminal box is provided above the connecting portion in communication with the electric motor housing, that an outer wall forming the terminal box and an outer wall forming the gearbox casing are used to form part of the breather chamber, and that part of a cover member which covers the terminal box is used as an upper wall of the breather chamber.
In this construction of the breather device, in addition to the above advantages, the breather chamber can be rendered compact in size. The outer wall of the terminal box and the outer wall of the gearbox casing are utilized to form part of the breather chamber, which is further covered by part of the cover member to form the breather chamber. In other words, by utilizing the outer wall of the terminal box and the outer wall of the casing the breather chamber is formed, leading to provision of a compact breather chamber without increasing the weight. Further, by disengaging the cover member of the terminal box the breather chamber is open and seen during the maintenance of the terminal box.
According to a third aspect of the invention, the aforementioned breather device according to the second aspect of the invention, the outer wall forming the terminal box extends such that an upper end thereof tilts toward the gearbox.
In this construction of the breather device, in addition to the above advantages, workability and assembly of the terminal box can be facilitated because the outer wall of the terminal box tilts and the open end of the terminal box obliquely faces upward. The dead space below the tilted terminal box is effectively utilized as the breather chamber. Therefore, the electric motor housing and the gearbox casing can be rendered compact in size.